Detection of carbon monoxide in ambient air with a piezoelectric crystal

Abstract

Carbon monoxide is first reacted with mercuric oxide at 210 C to produce mercury vapour. The mercury vapour liberated is then adsorbed on the gold electrode of the piezoelectric crystal, thereby increasing the mass on the crystal and decreasing its frequency of vibration. The change of frequency is proportional to the amount of mercury present and is indicative of the carbon monoxide content of the air. Reversibility can be achieved by thermal desorption. By use of a reference stream, the background due to the thermal decomposition of mercuric oxide is compensated. The effect of moisture and interferences from other reducing gases can be eliminated by use of a precolumn. The detector is simple, inexpensive, and portable. Concentrations in the part-per-million and part-per-billion ranges can be detected by varying the sample size.